How ocean water absorbs and scatters light (PACE)
What it measures. How ocean water and the things in it absorb and scatter light, broken into per-pixel optical properties like total absorption, backscattering, and the contribution from phytoplankton and dissolved matter. These describe the water itself, independent of sun angle or viewing angle.
How it's made. Retrieved from the PACE satellite's OCI instrument by taking its measurements of ocean-reflected light and running them through an optical model that separates the different light-affecting components.
How & where you'd use it. Used to classify water types, assess water clarity, study ocean biology and carbon, and compare results reliably across different satellites.
What's measured
Coverage & cadence
- Time span2024-03-05 → ongoing
- Measured byPACE (OCI)
- Processing levelLevel 2
- Spatial extent-180, -90, 180, 90
- FormatsnetCDF-4
- StatusACTIVE
What you can do with it
- Watch sea-surface temperature and marine heatwaves
- Spot algal blooms and ocean-colour shifts
- Support fisheries and coastal monitoring
Official description
The Inherent Optical Properties (IOP) suite provides per-pixel inherent optical properties - quantities that describe how seawater and its constituents absorb and scatter light, independent of illumination or viewing geometry. IOPs are retrieved from spectral Remote Sensing Reflectance (Rrs) using the default configuration of the Generalized Inherent Optical Properties (GIOP) model framework. These products support water-type classification, water-clarity assessment, biogeochemical studies, and forward/adjoint radiative-transfer applications, and they enable more robust cross-sensor comparisons than purely apparent (AOP) products. The hyperspctral band list is found in the science data file metadata. Geophysical variables in this suite include: - Kd - Diffuse attenuation coefficient of downwelling irradiance (m^-1) - a - Total absorption coefficient (sum of pure water + phytoplankton + CDOM/detritus, m^-1) - bb - Total backscattering coefficient (m^-1) - aph - Phytoplankton absorption coefficient (m^-1) - aph_unc_442 - Uncertainty in absorption due to phytoplankton at 442 nm (m^-1) - adg_442 - Combined CDOM + non-algal detritus absorption coefficient at 442nm (m^-1) - adg_unc_442 - Uncertainty in absorption due to gelbstoff and detrital material at 442 nm (m^-1) - bbp_442 - Particulate backscattering coefficient at 442nm (m^-1) - bbp_unc_442 - Uncertainty in particulate backscattering at 442 nm (m^-1) - rrsdiff - Fractional mean Rrs difference (reconstructed from inverted IOPs - input) (unitless) - l2_flags - Level-2 processing flags (bitmask; see per-variable attributes for flag_masks and flag_meanings)
Get the data
import earthaccess
earthaccess.login(strategy="netrc") # free Earthdata Login
results = earthaccess.search_data(
short_name="PACE_OCI_L2_IOP",
version="3.1",
bounding_box=(-122.5, 37.2, -121.8, 37.9), # your area (W,S,E,N)
temporal=("2024-01-01", "2024-12-31"), # your dates
)
files = earthaccess.open(results) # stream straight from OB_CLOUDBrowsing CMR needs no login. Downloading or streaming bytes needs a free Earthdata Login + the earthaccess package. Official links
- Earthdata Search allows users to search, discover, visualize, refine, and access NASA Earth Observation data. GET DATA
- View the version history of this product. VIEW RELATED INFORMATION
- NASA's Ocean Color Web - Data Distribution Site GET DATA
- PACE Homepage VIEW RELATED INFORMATION
- OCI Homepage VIEW RELATED INFORMATION
- Satellite data procesing can be difficult. We're here to help! Visit the Oceandata Help Hub to navigate learning content for accessing visualizing, and analyzing data products. VIEW RELATED INFORMATION
- Data structure file for processing level L2 VIEW RELATED INFORMATION
- Sample data file for processing level L2 VIEW RELATED INFORMATION